The trend in semiconductor technology to double the functional complexity of its products every 18 months (e.g., Moore's “law”) has several implicit consequences. First, the cost per functional unit should drop with each generation of complexity so that the cost of the product with its doubled functionality would increase only slightly. Second, the higher product complexity should largely be achieved by shrinking the feature sizes of the chip components while holding the package dimensions constant; preferably, even the package dimensions should shrink. And third, but not least, the increased functional complexity should be paralleled by an equivalent increase in reliability of the product.
The scaling of the components in the lateral dimension requires vertical scaling as well, so as to achieve adequate device performance. This vertical scaling requires the thickness of the gate dielectric, commonly silicon dioxide, to be reduced. Thinning of the silicon dioxide gate dielectric provides a smaller barrier to dopant diffusion from a polysilicon gate structure (or metal diffusion from a metal gate structure) through the underlying dielectric, often resulting in devices with diminished electrical performance (e.g., leakage) and reliability.
One well-established technique for mitigating the problems associated with silicon dioxide gate dielectrics includes using a nitrided gate dielectric (e.g., for example a silicon oxynitride gate dielectric, nitrided high-k dielectric, nitrided silicate gate dielectric, etc.) to raise the dielectric constant thereof. This allows the use of a thicker gate dielectric where a thinner dielectric would ordinarily be needed, providing for less leakage through the gate dielectric. Unfortunately, nitrided gate dielectrics are susceptible to having non-uniform nitrogen profiles therein, which negatively affect the reliability thereof.
Accordingly, what is needed in the art is a semiconductor device having a nitrided gate dielectric layer therein and a method of manufacture therefor which do not experience the drawbacks of the prior art.